SLEEP EFFECTS FOLLOWING INTRATHECAL ADMINISTRATION THE 5-HT1A AGONIST8-OH-DPAT AND THE NMDA ANTAGONIST AP-5 IN RATS

The modulating effect of an intrathecally (i.t.) administered 5-HT1A a gonist and an NMDA antagonist on sleep, waking and EEG power spectra w as investigated in rats. The 5-HT1A agonist 8-hydroxy-2-(di-n-propylam ino)tetralin (8-OH-DPAT) (38 nmol) increased total slow wave sleep (TS WS) and decreased waking over the 8 h recording period. The TSWS incre ase was mostly due to an increase in SWS1. Sleep latency to SWS1 was a lso reduced. The NMDA antagonist dl-2-amino 5-phosphonovaleric acid (A P-5) (31.5 nmol) reduced waking. SWS1 was increased, but TSWS was not changed. An increase in REM sleep was seen during the last part of the recording. Combined treatment with 8-OH-DPAT and AP-5 reduced waking and increased TSWS. No change in REM sleep was seen. There were no sys tematic changes in either waking, TSWS or REM fronto-frontal or fronto -parietal EEG power spectrum after any of the treatments. The results suggest that in the spinal cord stimulation of 5-HT1A receptors have a dampening effect on transmission of sensory information, leading to d eactivation and thereby increased possibilities for sleep induction. B lockade of the NMDA receptors may also lead to a small dampening of se nsory transmission with similar consequences.